Currently, the only way to conclusively diagnose the disorder during pregnancy is to take samples of genetic material from the fetus via amniocentesis or another method. But these methods come with a risk of miscarriage.

Other less invasive prenatal tests, such as nuchal translucency scans, can only estimate the risk of Down syndrome in the fetus.

DNA Differences in Down Syndrome

The new Down syndrome test is based on differences in DNA methylation patterns, which are critical to gene expression, between the mother and the fetus. It screens for extra copies of a fetal chromosome in the mother’s blood.

In Down syndrome, there are three copies of chromosome 21, called trisomy-21, instead of the normal two.

Researchers say the method is fast and easy to perform in any genetic diagnostic lab and does not require special or expensive equipment.

“Such a noninvasive approach will avoid the risk of miscarriages of normal pregnancies caused by current, more invasive procedures,” write researcher Elisavet A. Papageorgiou, of the Cyprus Institute of Neurology and Genetics in Nicosia, Cyprus, and colleagues in Nature Medicine.

“Nevertheless, a larger-scale study will need to be performed to assist in the introduction of the diagnostic strategy into the clinical practice of prenatal diagnostic laboratories.”